Stent delivery catheter system for primary stenting

ABSTRACT

The present invention relates to an expandable tubular device for implantation in the lumen of a body duct, such as a blood vessel in particular, in order to ensure a passage therein, said device consisting of an assembly of tubular elements aligned along a common longitudinal axis and successively joined together in parts by a plurality of liking members, each tubular element consisting of a strip forming a zigzag corrugation defining bent extreme portions which are sucessively connected together in pairs in opposite directions by rectilinear intermediate portions, the thickness (e) of said strip forming each of the above-mentioned tubular elements ( 1 ), measured radially relative to said tubular element, being greater than the width  1  of this strip in said bent potions ( 2 ).

FIELD OF USE

[0001] This invention is in the field of catheters to place stents intoa stenosis in a vessel of a human body.

BACKGROUND OF THE INVENTION

[0002] Intravascular stents are well known in the field ofinterventional cardiology for the treatment of arterial stenoses. Whenplaced through the body's vascular system, most stents are mounted ontoa balloon angioplasty catheter with or without a cylindrical sheath thatcovers the stent prior to stent deployment by balloon expansion at thesite of a dilated stenosis. If a sheath is not used, the stent can getcaught on a calcified plaque or on the guiding catheter during movementinto or out of the patient's body. This can cause the stent to come offthe delivery catheter and embolize into the vasculature. When a sheathis used, it can have a few disadvantages. A first disadvantage is thatmost prior art sheaths are secured only at the stent delivery catheter'sproximal end. Therefore, in order to have sufficient column strength,the sheath must be relatively thick-walled, making it stiff and bulky sothat passage through tortuous coronary arteries can be difficult.Another disadvantage of prior art sheaths is that they have blunt distalends that can catch on an already deployed stent, or on a calcifiedpiece of intimal dissected tissue or on a tight stenosis. Still further,when secured only at the proximal end of a stent delivery catheter, thesheath often either uncovers the stent due to significant bending of thestent delivery catheter or the sheath advances too far distally beyondthe distal end of the stent.

[0003] Because of the comparatively larger diameter, blunt end andstiffness of extant sheathed stent delivery systems or because of therough outer surface of unsheathed stent delivery systems, pre-dilatationwith another balloon angioplasty catheter is almost always requiredbefore stent implantation. It is highly desirable to be able to delivera stent without pre-dilatation. The procedure of deploying a vascularstent without pre-dilatation and post-dilatation is called “primarystenting”. In U.S. Pat. No. 5,792,144, Fischell et al describe a primarystenting system having a membrane sheath over the distal section of thecatheter which holds the stent. While the Fischell device provides thecapability for primary stenting, it may not hold the distal end of themembrane sheath with sufficient firmness to prevent it from uncoveringthe stent during passage through curved or calcified vessels. Inaddition, the membrane sheath of the Fischell et al invention addsseveral thousandths of an inch to the stent system profile. It would beadvantageous if the stent delivery systems' outside diameter could bemade smaller by shrinking the membrane sheath down onto the stent or,alternatively, having a primary stenting system without a membranesheath.

SUMMARY OF THE PRESENT INVENTION

[0004] The present invention is a stent delivery catheter system forplacing a stent within a stenosis in a vessel of a human body withoutthe need for either pre-dilatation of the stenosis or post-dilatation ofthe stent. The primary stenting delivery catheter system utilizes thecombination of low profile (i.e., a small outer diameter) with acontinuous, smooth and lubricious outer surface extending backward froma tapered distal tip. This design makes it possible for the stentdelivery catheter to be pushed through even very tight stenoses withoutrequiring pre-dilatation.

[0005] Two versions of the primary stent delivery system are envisioned.The first version is a sheathed primary stenting system with a two-partsheath having a thick-walled proximal section and an ultra-thin distalsection that is shrunk down to secure it to the catheter's distal tip.This embodiment differs from the prior art Fischell et al device thatdoes not shrink its membrane sheath down over the stent and over theballoon catheter's distal tip.

[0006] For the first version which is a sheathed primary stentingsystem, the preferred embodiment of the ultra-thin distal sheath sectionof the sheathed system uses heat shrinkable elastomer tubing with a wallthickness that is less than 0.05 mm and may be less than 0.025 mm. Thereare two methods for securing the ultra-thin distal sheath section overthe distal tip. A preferred method is to employ another thin tube shrunkdown over the distal end of the ultra-thin distal sheath. It is alsoenvisioned that simply shrinking the ultra-thin distal sheath sectiondown on the tapered section of the distal tip will hold it securely. Amonorail (rapid exchange) version of this stent delivery system is alsoenvisioned.

[0007] The second version of the present invention is an unsheathedprimary stenting system. The unsheathed primary stenting system usesradiopaque elastic bands mounted over the ends of the balloon justproximal and just distal to the stent to provide the lowest possibleprofile for a primary stent delivery system without the risk of stentembolization. These radiopaque elastic bands could contain ahigh-density material such as tungsten to make them radiopaque andeliminate the need for radiopaque markers normally attached to theangioplasty balloon inner shaft which markers can increase the deviceprofile.

[0008] Thus, an object of this invention is to have a low profileprimary stenting system that has a sheath with an ultra-thin distalsection that is shrunk down over the stent and over the distal tip ofthe catheter.

[0009] Another object of this invention is to have a sheathed primarystenting system with an outer diameter, i.e., a profile of less than 1.1mm.

[0010] Still another object of this invention is to have a primarystenting system with a sheath having a distal section with wallthickness of less than 0.05 mm.

[0011] Still another object of this invention is to have a primarystenting system with a sheath having a distal section with wallthickness of less than 0.025 mm.

[0012] Still another object of this invention is to have a primarystenting system with a sheath having a distal section that is made froma heat shrinkable or solvent swelled elastomer tubing.

[0013] Still another object of this invention is to have a primarystenting system with a sheath having a distal section that is made froma nylon material.

[0014] Still another object of this invention is to have a primarystenting system with a sheath that is lubricity coated.

[0015] Still another object of this invention is to utilize elastictubes placed just proximal and just distal to the stent as a means toprevent stent embolization for an unsheathed primary stenting system.

[0016] Still another object of this invention is to have a stentdelivery catheter system that utilizes a gently tapered, lubriciouscoated, highly flexible elastomer tip in order to have a distal sectionof the stent delivery catheter system that can be readily pushed througha tight stenosis.

[0017] Still another object of this invention is to have a primarystenting system that can place a stent into a tight stenosis withoutfirst pre-dilating that tight stenosis.

[0018] Still another object of this invention is to have a sheathedprimary stenting system with rapid exchange capability.

[0019] These and other objects and advantages of this invention willbecome apparent to a person of ordinary skill in this art upon carefulreading of the detailed description of this invention including thedrawings as presented herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a longitudinal cross section of a sheathed primarystenting system that illustrates the structure of the proximal anddistal sections of the primary stenting system.

[0021]FIG. 2A shows a longitudinal cross section of the distal sectionof the stent delivery catheter system prior to stent deployment as it ispushed through an arterial stenosis.

[0022]FIG. 2B shows a longitudinal cross section of the distal sectionof the stent delivery catheter system prior to stent deployment as itwould be placed into an arterial stenosis.

[0023]FIG. 2C is a longitudinal cross section of the distal section ofthe stent delivery catheter system with the sheath pulled back thusuncovering the stent.

[0024]FIG. 2D shows a longitudinal cross section of the distal sectionof the stent delivery catheter system with the balloon inflated and thestent deployed outward so as to dilate the stenosis.

[0025]FIG. 2E is a longitudinal cross section of the dilated stenosisshowing the stent deployed radially outward and the stent deliverycatheter system removed from the patient's artery.

[0026]FIG. 3 is a longitudinal cross section of the distal portion ofthe an alternative embodiment of the sheathed primary stenting system

[0027]FIG. 4 is a longitudinal cross section of the distal portion of anunsheathed embodiment of the primary stenting system.

[0028]FIG. 5A is a longitudinal cross section of the distal portion ofan alternative embodiment of the sheathed primary stenting system.

[0029]FIG. 5B is a longitudinal cross section of a minor variation ofthe distal portion of the sheathed primary stenting system of FIG. 5A.

[0030]FIG. 6 is a longitudinal cross section of the central and distalportions of a rapid exchange version of the sheathed primary stentingsystem.

[0031]FIG. 7 is a side view of the central portion of the rapid exchangeversion of the sheathed primary stenting system as shown in FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a longitudinal cross section of a primary stentingsystem 10 shown in its pre-deployment configuration that is formed intwo sections, namely; a proximal section 5 and a distal section 6. Theprimary stenting system 10 consists of a balloon angioplasty catheter20, a slideable sheath 30, a stent 40 and a guide wire 50.

[0033] The balloon angioplasty catheter 20 consists of an outer shaft11, an inner shaft 12, a proximal radiopaque marker band 13P, a distalradiopaque marker band 13D, a proximal elastomer band 14P, a distalelastomer band 14D, an inflatable angioplasty balloon 18 and a graduallytapered elastomer distal tip 15. The gradually tapered distal tip 15 hasa gradually tapered proximal portion 15P and a gradually tapered distalportion 15D. The gradually tapered distal tip 15 has an average taperangle 24 that is typically less than 4 degrees and may be under 1 degreefor devices designed for small diameter blood vessels. At the proximalend of the balloon angioplasty catheter 20 is a luer fitting 23 throughwhich the guide wire 50 can be passed into the central lumen 19 of theinner shaft 12. Also at the proximal end of the balloon angioplastycatheter 20 is a side arm 21 having a luer fitting 22 and a centralpassageway 26. The central passageway 26 is in fluid communication withthe annular passageway 17 that lies between the inner surface of theouter shaft 11 and the outer surface of the inner shaft 12. The balloonangioplasty catheter 20 also has at its distal section 6 an angioplastyballoon 18 whose interior chamber 29 is in fluid communication with theannular passageway 17 and the central lumen 26 of the side arm 21. Thusa source of inflation fluid can be inserted into or removed from thelumen 26 to inflate and deflate the balloon 18. Mounted on the balloon18 is a balloon expandable stent 40 of any design that is well known inthe art of balloon expandable stents.

[0034] The slideable sheath 30 is situated coaxially about the balloonangioplasty catheter 20. The sheath 30 has a Tuohy-Borst fitting 36 atthe proximal end of the sheath 30, an ultra-thin distal section 34 and asheath proximal section 32 having a proximal end attached to theTuohy-Borst fitting 36 and a distal end attached to the ultra-thindistal section 34. The Tuohy-Borst fitting 36 has a main body 31 havinga side arm 39 with a luer fitting 33. The side arm 39 has a centrallumen 38 that is in fluid communication with the annular passageway 27that lies between the interior surface of the sheath proximal section 32and the exterior surface of the outer shaft 11. The main body 31 of theTuohy-Borst fitting has a threaded proximal end onto which a nut 35 canbe screwed on or off. Advancing the nut 35 compresses the elastomergland 37 thus causing a fluid seal to be made against the outer surfaceof the outer shaft 11. When such a fluid seal exists, liquid can beinjected through the lumen 38 of the side arm 39 to flush air out of theannular passageway 27.

[0035] The ultra-thin distal section 34 is shrunk down onto the proximalelastomer band 14P, the stent 40, the distal elastomer band 14D and theproximal portion 15P of the gradually tapered distal tip 15. A securingtube 16 fixedly attached at its distal end to the distal tip 15 isshrunk tight down over the distal portion of the ultra-thin distalsection 34 thereby securing it during delivery of the primary stentingsystem 10 into the human body. Although the securing tube 16 holds theultra-thin distal section 34 against the distal tip 15, the ultra-thindistal section 34 can still be pulled proximally out from under thesecuring tube 16 so as to unsheathe the stent 40. It should be notedthat the distal tip 15 is molded so that there will be a continuousouter surface at the transition 8 from the distal tip 15 to the securingtube 16.

[0036] The sheath proximal section 32 has a distal end 9 that is incontact with the proximal end of the proximal elastomer band 14P. Thiscauses the push force exerted at the proximal end of the sheath 30 to betransferred from the sheath proximal section 32 through the proximalelastomer band 14P, stent 40 and distal elastomer band 14D to the distaltip 15 thereby enhancing penetration through a tight stenosis. Inaddition to providing a transfer of push force, the elastomer bands 14Pand 14D will prevent the stent 40 from sliding in either a proximal ordistal direction and therefore reduce the probability of stentembolization. The elastomer bands 14P and 14D are typically made from ahighly elastic material such as polyurethane or silicone rubber.

[0037] The sheath 30 is pulled back during stent deployment by firstloosening the nut 35 of the Tuohy-Borst fitting 36, then sliding theTuohy-Borst fitting 36 in a proximal direction (as shown by the arrow 7)while holding fixed the luer fitting 23 at the proximal end of theballoon angioplasty catheter 20. This will retract the ultra-thin distalsection 34 from under the securing tube 16 and pull it back far enoughbeyond the proximal end of the angioplasty balloon 18 so as to positionthe distal end of the ultra-thin distal section 34 proximal to theproximal end of the balloon 18. This will allow balloon expansion of thestent 40. The system 10 dimensions are such that the stent 40 iscompletely uncovered when the Tuohy-Borst fitting 36 is pulled backuntil it is in close proximity to the side arm 21 at the proximal end ofthe balloon angioplasty catheter 20.

[0038] It is envisioned that the ultra-thin distal section 34 of thesheath 30 would have a wall thickness of less than 0.05 mm and may beconstructed with wall thickness of 0.025 mm or less.

[0039] Current state of the art angioplasty balloons are beingconstructed with a maximum pre-deployment diameter of less than 0.75 mm.Assuming a wall thickness of 0.12 mm for the stent 40 to obtain goodradiopacity and a thickness for the ultra-thin distal section 34 of thesheath 30 of 0.05 mm, the outside diameter of the primary stentingsystem would be less than 1.1 mm.

[0040] The gradually tapered distal tip 15 would typically be 1 to 4 cmlong with a taper angle 24 that is typically less than 4 degrees and canbe less than 1 degree. The gradually tapered proximal portion 15P of thedistal tip 15 should be 25% to 75% of the length of the entire distaltip 15.

[0041] The balloon angioplasty catheter 20 is made from standardmaterials as is well known in the art of balloon angioplasty. The stent40 is typically constructed from stainless steel. The stent may becoated with a drug for delivery to the wall of the vessel or may containa radioisotope. The drug and/or radioisotope may be used to prevent theformation of neointimal hyperplasia that results from stent implantationinto the wall of a blood vessel. The proximal section 32 of the sheathcan be constructed from an elastomer such as nylon or urethane, or anelastomer with fine wires wound or braided into the sheath material.

[0042] Heat shrinking and solvent swelling processes are two alternativemeans for shrinking down the ultra-thin distal section 34 of the sheath30. If heat shrinking is used, the ultra-thin distal section 34 of thesheath would typically be constructed from a material such as the nylonthat is used for angioplasty balloons. Such a material could be heatshrunk down over the stent 40 and proximal section 15P of the distal tip15. If solvent swelling is used, the ultra-thin distal section 34 of thesheath would typically be constructed from a plastic such aspolyurethane, Teflon or polyethylene which can be solvent swelled andthen shrunk down as the solvent evaporates onto the stent 40 andproximal section 15P of the distal tip 15. The same types of materialsand shrinking processes could be used for the securing tube 16.

[0043] To facilitate penetration through a tight stenosis, the graduallytapered distal tip 15, securing tube 16 and ultra-thin distal section 34of the sheath 30 should be lubricity coated.

[0044] The operation of the primary stenting system 10 is best explainedwith the assistance of FIGS. 2A, 2B, 2C, 2D and 2E.

[0045]FIG. 2A shows the distal section 6 advanced over the guide wire 50until the tapered tip 15 has begun penetration of an arterial stenosis.It should be understood that the very gradually tapered shape of the tip15 and the continuous outer surfaces of the tip 15, securing tube 16 andultra-thin distal sheath section 34 (each of which can have a lubriciousouter coating) facilitates entry into an arterial stenosis.

[0046]FIG. 2B shows the distal section 6 with the non-deployed stent 40centered within an arterial stenosis. The radiopaque marker bands 13Pand 13D are utilized to center the stent 40 with respect to thestenosis.

[0047] A most important capability of the primary stenting system 10 isits ability to be pushed through even a very tight stenosis. Thiscapability originates from several specific aspects of the design of theprimary stenting system 10, namely, the extraordinarily gradual taper ofthe lubricity coated distal tip 15, the continuous outer surfaces of thetip 15, securing tube 16 and ultra-thin distal sheath section 34, andthe distally directed push force that can be transferred to the distaltip 15 from the distal end 9 of the sheath's proximal section 32. Thesystem 10 obtains its capability to push the distal tip 15 through atight stenosis by a series of structures each of which is capable ofsignificant pushability. This series of structures that provideexcellent pushability for the primary stenting system 10 are:

[0048] (1) The Tuohy-Borst fitting 36 at the proximal end of the sheath30 which fitting lies outside the patient's body.

[0049] (2) The comparatively thick-walled, flexible tube forming thesheath proximal section 32 that is typically a composite cylinder madefrom wire and an elastomer.

[0050] (3) The proximal elastic tube 14P that is attached to theproximal end of the angioplasty balloon 18 which transmits the pushforce from the distal end of the sheath proximal section 32.

[0051] (4) The stent 40 which is the next structure that transmits thedistally directed push force toward the distal tip 15.

[0052] (5) The distal elastomer tube 14D attached to a distal portion ofthe balloon 18 that next transmits the push force to the distal tip 15is the last link in the pushability chain that enhances the capabilityof the primary stenting system 10 to push through a tight stenosis.

[0053] In summary, the pushability of the sheath 30 as transferred to adistal portion of the balloon angioplasty catheter 10 can be very muchgreater than the pushability of the outer shaft 11 and inner shaft 12 bythemselves. It should be noted that the design of the primary stentingsystem 10 allows the distal sheath section 34 to be both verythin-walled and highly flexible and not requiring any contribution topushability.

[0054] The thin-walled, flexible design of the ultra-thin distal sheathsection 34 provides improved capability of the system 10 to place thestent 40 in a tight arterial stenosis because its flexibility improvespassage through the tortuous vasculature of coronary arteries. Inaddition, since the ultra-thin distal sheath section 34 need notcontribute to system pushability, a wall thickness of 0.05 mm or lesscan be used. This minimizes the outside diameter (profile) of the system10 thus again improving the system's capability for placing the stent 40into a tight stenosis.

[0055]FIG. 2C shows the sheath 30 pulled back so the distal end of theultra-thin distal section 34 is proximal to the proximal end of theballoon 18 and the stent 40 is uncovered and therefore ready to beexpanded. Pull back of the sheath 30 is accomplished by holding the Luerfitting 23 at the proximal portion of the stent delivery catheter 10fixed while pulling back on the nut 35 of the Tuohy-Borst fitting at thedistal portion of sheath 30. This is accomplished after the nut 35 isloosened so that the gland 37 slides easily over the outer shaft 11 ofthe balloon angioplasty catheter 20.

[0056]FIG. 2D shows an inflated balloon 18′ that causes the deployedstent 40′ to dilate the stenosis. It should be noted that the elastomertubes 14P′ and 14D′ become distorted when the balloon 18 is inflated.After the balloon 18′ is deflated, the tubes 14P′ and 14D′ revert totheir original shape as shown for the tubes 14P and 14D shown in FIGS.1, 2A, 2B and 2C.

[0057]FIG. 2E shows the stent 40′ in place with the balloon angioplastycatheter 20, sheath 30 and guide wire 50 removed from the patient'sarterial system.

[0058]FIG. 3 is a longitudinal cross section of an alternativeembodiment of the present invention. FIG. 3 shows the distal section ofa sheathed primary stenting system 60 in its pre-deploymentconfiguration. In this embodiment the sheath 30 is identical to that ofthe primary stenting system 10 of FIGS. 1 through 2D inclusive: Theballoon angioplasty catheter 55 has a gradually tapered distal tip 65with gradually tapered proximal portion 65P and gradually tapered distalportion 65D. The balloon angioplasty catheter 55 lacks the securing tube16 which was attached to the gradually tapered distal tip 15 of theballoon angioplasty catheter 20 of FIGS. 1 through 2D inclusive. In theFIG. 3 embodiment, the distal end of the ultra-thin distal section 34 isshrunk down onto the proximal portion 65P of the gradually tapereddistal tip 65 and forms a continuous outer surface transition from thegradually tapered distal portion 65D of the tapered tip 64. Otherwise,the proximal end and function of the primary stenting system 60 isidentical to the primary stenting system 10 of FIGS. 1 though 2Dinclusive. It should be noted that having the ultra-thin distal section34 of the sheath 30 shrunk down over the entire proximal portion 65P ofthe tapered tip 65 will help keep the distal end of the ultra-thindistal section 34 secured during advancement through curved vessels.

[0059]FIG. 4 is a longitudinal cross section of another alternativeembodiment of the present invention. FIG. 4 shows the distal section ofa primary stenting system 80 in its pre-deployment configuration. Inthis embodiment there is no sheath 30 as in the embodiments of FIGS. 1and 3. In the FIG. 4 embodiment, the primary stenting system has a stent40, a balloon angioplasty catheter 70 and a guide wire 50. The proximalend of the balloon angioplasty catheter 70 is identical to the proximalend of the balloon angioplasty catheter 20 of FIG. 1. Furthermore, theballoon angioplasty catheter 70 consists of an outer shaft 11, an innershaft 12, a proximal radiopaque elastomer band 74P, a distal radiopaqueelastomer band 74D and a distal elastomer tapered tip 75. The balloonangioplasty catheter 70 has a central lumen 19 and an annular ballooninflation lumen 17. The balloon angioplasty catheter 70 also has anangioplasty balloon 78 whose interior chamber 79 is in fluidcommunication with the annular balloon inflation lumen 17. Mounted onthe balloon 78 is a balloon expandable stent 40 of any design that iswell known in the art of balloon expandable stents. The radiopaqueelastomer bands 74P and 74D eliminate the need for separate radiopaquemarker bands 13P and 13D of the balloon angioplasty catheter 20 ofFIG. 1. Eliminating the internal radiopaque marker bands 13P and 13Dallows a lower profile for the system 60. The elastomer bands 74P and74D are typically made from a highly elastic material such aspolyurethane or silicone rubber into which a high density material suchas tungsten (typically in powdered form) has been mixed.

[0060] It should be understood that radiopaque elastomer bands 74P and74D of FIG. 4 could be used in the place of elastomer bands 14P and 14Din the previous embodiment 10 shown in FIGS. 1 through 2E inclusive orin the embodiment 60 shown in FIG. 3. If the radiopaque elastomer bands74P and 74D are used in system 10 or 60 they eliminate the need forseparate radiopaque marker bands 13P and 13D and make the system 10 or60 lower in profile than if the bands 13P and 13D were present

[0061]FIG. 5A is a longitudinal cross section of the distal portion ofanother alternative embodiment of the present invention which is aprimary stenting system 100A shown in its pre-deployment configuration.The primary stenting system 100A consists of a balloon angioplastycatheter 110, a slideable sheath 120, a stent 140 and a guide wire 50.

[0062] The balloon angioplasty catheter 110 consists of an outer shaft111, an inner shaft 112, a proximal radiopaque marker band 113P, adistal radiopaque marker band 113D, an elastomer band 114 and a sheathsecuring tube 115. The distal end of the sheath securing tube 115 isfixedly attached to the distal end of the inner shaft 112 of the balloonangioplasty catheter 110. The balloon angioplasty catheter 110 also hasa folded angioplasty balloon 118 whose interior chamber 129 is in fluidcommunication with the annular passageway 117 used for ballooninflation. Although the folds of the balloon 118 are shown in FIG. 5A,the balloon 118 is not substantially different from the balloon 18 ofFIG. I where the folds are not shown. Both balloons 18 and 118 aretypical of angioplasty balloons that are well known in the art ofballoon angioplasty. In this embodiment, the distal tip 116 is thedistal extension of the inner shaft 112 beyond the distal end of theballoon 118.

[0063] Mounted on the balloon 118 is a balloon expandable stent 140 ofany design that is well known in the art of balloon expandable stents.The proximal and distal radiopaque markers 113P and 113D are swaged intothe inner shaft 112 so as to not protrude against the angioplastyballoon 118 thus providing a minimum profile for the system 10A.

[0064] The slideable sheath 120 is situated coaxially about the balloonangioplasty catheter 110. The distal portion of the sheath 120 shown inFIG. 5A comprises an ultra-thin distal section 124 and a sheath proximalsection 122. The proximal section 122 of the sheath 120 is identical tothe proximal section 32 of the sheath 30 of FIG. 1.

[0065] The ultra-thin distal section 124 of the sheath 120 is shrunkdown onto the elastomer band 114, the stent 140, the distal end of theballoon 118 and part of the inner shaft 112. The distal end of thesecuring tube 115 is fixedly attached to the distal end of the distalsection 116. The proximal section of the securing tube 115 is tightlyshrunk down over the distal portion of the ultra-thin distal section 124of the sheath 120. This will secure the distal end of the ultra-thindistal section 124 to the inner shaft 112 and create an extremely smoothouter surface for easy sliding around tight curves and for penetrationthrough tight stenoses during delivery of the primary stenting system100A into the human body. Although the securing tube 115 holds theultra-thin distal section 124 against the inner shaft 112, theultra-thin distal section 124 can still be pulled proximally out fromunder the securing tube 1 15 so as to uncover the stent 140.

[0066] The sheath proximal section 122 has a distal end 9 that is incontact with the proximal end of the elastomer band 114. This causes thepush force exerted at the proximal end of the sheath 120 to betransferred from the sheath proximal section 122 through the proximalelastomer band 114 to the distal end of the balloon angioplasty catheter110. In addition to providing a transfer of push force, the elastomerband 114 will prevent the stent 140 from sliding in a proximal directionduring pullback of the sheath 120. The elastomer band 114 is typicallymade from a highly elastic material such as polyurethane or siliconerubber.

[0067] Methods for attaching the distal end of the sheath securing tube1 15 to the distal end of the inner shaft 112 include ultrasonic weldingand adhesive bonding.

[0068] It should be understood that the radiopaque marker bands 13P and13D of FIGS. 1 through 2D inclusive could be swaged onto the inner shaft11 like the radiopaque marker bands 113P and 113D of the system 100A ofFIG. 5A. Swaged radiopaque marker bands could also be used with theunsheathed primary stenting system 80 of FIG. 4 in which case theelastomer bands 74P and 74D need not contain a radiopacity enhancingmaterial.

[0069] The process for assembling the primary stenting system 100A ofFIG. 5A, where heat shrinking is used to contract the ultra-thin distalsection 124, is as follows:

[0070] 1. Assemble separately the balloon angioplasty catheter 110without the elastomer band 114.

[0071] 2. Assemble the proximal end and proximal section 122 of thesheath 120.

[0072] 3. Manufacture the stent 140.

[0073] 4. Insert the distal end of the balloon angioplasty catheter 110into the proximal end of the sheath 120 and slide the proximal end ofthe sheath 120 as far as it can go toward the proximal end of theballoon angioplasty catheter 110.

[0074] 5. Place the elastomer band 114 over the proximal end of theballoon 118.

[0075] 6. Crimp the stent 140 onto the balloon 118 of the balloonangioplasty catheter 110 just distal to the distal end of the elastomerband 114.

[0076] 7. Slide the proximal end of the ultra-thin distal section 124over the distal portion of the balloon angioplasty catheter 110 withstent 140 until the proximal end of the ultra-thin distal section 124lies just proximal to the distal end of the proximal sheath 122.

[0077] 8. Fixedly attach by welding or bonding the ultra-thin distalsection 124 to the proximal sheath 122.

[0078] 9. Slide the now joined two part sheath distally until the distalend 9 of the proximal sheath 122 touches the proximal end of the markerband 114.

[0079] 10. Shrink the ultra-thin distal section 124 down onto elastomerband 114, crimped stent 140, and a portion of the extension of the innershaft 112 beyond the distal end of the balloon 118.

[0080] 11. Trim any excess length of ultra-thin distal section 124 untilthe distal end of the ultra-thin distal section is located at thedesired position on the extension of the inner shaft 112 beyond thedistal end of the balloon 118.

[0081] 12. If a securing tube 115 is used, slide it over and shrink itdown onto the distal end of the balloon angioplasty catheter 110 anddistal end of the shrunk ultra-thin distal section 124.

[0082] 13. Fixedly attach by welding or bonding, the distal end of thesecuring tube 115 to the distal end of the distal section 116 of theinner shaft 112.

[0083] The system 100A is now ready for final packaging andsterilization.

[0084]FIG. 5B is a longitudinal cross section of the distal portion ofanother embodiment of the sheathed primary stenting system 100B which isa minor variation of the distal portion of the sheathed primary stentingsystem 100A of FIG. 5A. The only difference between the system 100B ofFIG. 5B and the system 100A of FIG. 5A is the securing tube 115 of FIG.5A which is not present in the system 100B of FIG. 5B.

[0085]FIG. 6 is a longitudinal cross section of the central and distalportions of a rapid exchange sheathed primary stenting system 200 shownin its pre-deployment configuration.

[0086] The rapid exchange primary stenting system 200 consists of aballoon angioplasty catheter 210, a slideable sheath 220, a stent 240and a guide wire 50.

[0087] The balloon angioplasty catheter 210 consists of a proximal shaft202 with inflation lumen 206 connected to a distal dual lumen shaft 212with inflation lumen 217 and guide wire lumen 219. The inflation lumen206 of the proximal shaft 202 is in fluid communication with theinflation lumen 217 of the dual lumen shaft 212. The guide wire lumen219 has its proximal end at the junction of the proximal shaft 202 anddual lumen shaft 212. The distal end of the dual lumen shaft 212 isconnected to a distal guide wire tube 211 so that the guide wire lumen219 of the dual lumen shaft 212 connects to the lumen 239 of the distalguide wire tube 211.

[0088] A proximal radiopaque marker band 213P and a distal radiopaquemarker band 213D are swaged onto the distal guide wire tube 211. Theballoon angioplasty catheter 210 has a folded angioplasty balloon 218whose interior chamber 229 is in fluid communication with the lumen 217used for balloon inflation. The proximal end of the angioplasty balloon218 is attached to the outside of the dual lumen shaft 212. The distalend of the balloon 218 is attached to the distal guide wire tube 211.Mounted on the balloon 218 is a balloon expandable stent 240 of anydesign that is well known in the art of balloon expandable stents.

[0089] An elastomer band 214 is placed over the proximal end of theballoon 218 and the distal end of the dual lumen shaft 212. A sheathsecuring tube 215 has its distal end attached to the distal end of thedistal guide wire tube 211 of the balloon angioplasty catheter 210.

[0090] The slideable sheath 220 is situated coaxially about the balloonangioplasty catheter 210 and has three sections, a proximal section 204,a central section 222 and an ultra-thin distal section 224. The distalend of the proximal section 204 is fixedly attached to the proximal endof the central section 222 of the sheath 220. The distal end of thecentral section 222 is attached to the proximal end of the ultra-thindistal section 224. An elongated hole 208 in the central section 222 ofthe sheath 220 allows the guide wire 50 to exit and extend proximallyoutside of the proximal section 204 thereby creating a rapid exchange ormonorail configuration for the sheathed primary stenting system 200. Theproximal end of the sheath 220 is similar to that of the sheath 30 ofFIG. 2.

[0091] The ultra-thin distal section 224 is shrunk down onto theelastomer band 214, the stent 240, the distal end of the balloon 218 andthe distal end of the guide wire tube 211. The distal end of a securingtube 215 is fixedly attached to the distal end of the guide wire tube211. The proximal section of the securing tube 215 is shrunk tight downover the distal portion of the ultra-thin distal section 224 of thesheath 220. This secures the distal end of the ultra-thin distal section224 to the guide wire tube 211 and creates an extremely smooth outersurface for passage through tortuous coronary vasculature and forpenetration through tight stenoses during delivery of the primarystenting system 200. Although the securing tube 215 holds the ultra-thindistal section 224 against the guide wire tube 211, the ultra-thindistal section 224 can still be pulled proximally out from under thesecuring tube 215 so as to uncover the stent 240.

[0092] The sheath central section 222 has a distal end 209 that is incontact with the proximal end of the elastomer band 214. This causes thepush force exerted at the proximal end of the sheath 220 to betransferred from the sheath proximal section 204 to the sheath centralsection 222 through the proximal elastomer band 214 to the distal end ofthe balloon angioplasty catheter 210. In addition to providing atransfer of push force, the elastomer band 214 prevents the stent 240from sliding in a proximal direction during pullback of the sheath 220.The elastomer band 214 is typically made from a highly elastic materialsuch as polyurethane or silicone rubber.

[0093] The dual lumen shaft 212 of the balloon angioplasty catheter 210is typically 2 to 20 cm long. This places the exit of the guide wire 50from the guide wire lumen 219 at the proximal end of the dual lumenshaft 212 approximately 4 to 24 cm from the distal end of the balloonangioplasty catheter 210.

[0094]FIG. 7 is a side view of the central portion of the rapid exchangeversion of the sheathed primary stenting system 200 of FIG. 6 in itspre-deployment configuration. The portions of the balloon angioplastycatheter 210 shown in FIG. 7 are the proximal shaft 202 and the duallumen shaft 212. In FIG. 7 the exit of the guide wire 50 from theproximal end of the dual lumen shaft 212 through the hole 208 in thecentral section 222 of the sheath 220 is clearly seen. The sheath 220can be pulled back a distance equal to the stent length plus severalcentimeters to uncover the stent 50. Even when the sheath 220 is pulledback over some of the guide wire 50 that extends outside the sheath 220,the proximal section of the guide wire 50 will continue to exit from thehole 208 of the central section 222 of the sheath 220. This designpermits the primary stenting system 200 to operate as a rapid exchangedevice.

[0095] Although the primary stenting systems 10, 60, 80, 100A and 200 asshown in FIGS. 1 through 7 inclusive are most valuable for stenting ofstenosis in coronary arteries, it should be understood that thesesystems can be used in any vessel of the human body. It should also benoted that the primary stenting systems 10, 60, 80, 100A and 200 caneach be readily used in tight arterial stenoses without requiringpre-dilatation. This capability for stent insertion withoutpre-dilatation saves both time and cost when placing stents into anarterial stenosis. It should also be noted that the elastomer bands 14Pand 14D of the systems 10 and 60 and the radiopaque elastomer bands 74Pand 74D of the system 80 exactly center the stent 40 on the balloons 18and 78 respectively.

[0096] All of the above embodiments provide excellent protection frominadvertent stent loss and embolization during a procedure. Thisadvantage makes the present invention of particular importance when thestents used are radioactive as described by Fischell et al in U.S. Pat.No. 5,059,166.

[0097] Various other modifications, adaptations, and alternative designsare of course possible in light of the above teachings. Therefore, itshould be understood at this time that within the scope of the appendedclaims, the invention could be practiced otherwise than as specificallydescribed herein.

What is claimed is:
 1. A pre-deployment configuration for a primarystenting system for placing a stent within a stenosis of a vessel in ahuman body, the system comprising: a flexible guide wire; a balloonangioplasty catheter having a distal portion, the balloon angioplastycatheter having an inflatable balloon located at its distal portion, theinflatable balloon having a proximal end and a distal end, the balloonangioplasty catheter also having a lumen through which the guide wirecan be slideably moved, the balloon angioplasty catheter also having adistal tip which extends in the distal direction from the distal end ofthe balloon to the distal end of the balloon angioplasty catheter, thedistal tip having a proximal end and a distal end, a stent coaxiallymounted around the inflatable balloon of the balloon angioplastycatheter the stent having a proximal end and a distal end; and a sheathgenerally in the form of a cylindrical tube that is coaxially locatedaround the balloon angioplasty catheter with its coaxially mountedstent, the sheath having a proximal section and an ultra-thin distalsection, the proximal section of the sheath having a proximal end and adistal end, the ultra-thin distal section of the sheath having aproximal end and a distal end, the proximal end of the ultra-thin distalsection of the sheath being fixedly attached to the distal end of theproximal section of the sheath, the ultra-thin distal section of thesheath being shrunk down onto the distal portion of the balloonangioplasty catheter including its coaxially mounted stent, the sheathbeing adapted to be slideably retracted in a proximal direction so thatthe distal end of the ultra-thin section of the sheath lies proximal tothe balloon so that the stent can be radially expanded when the balloonis inflated.
 2. The system of claim 1 wherein the wall thickness of theproximal section of the sheath is more than twice the wall thickness ofthe ultra-thin distal section.
 3. The system of claim 1 wherein the wallthickness of the ultra-thin distal section of the sheath is less than0.05 mm.
 4. The system of claim 1 wherein the wall thickness of theultra-thin distal section of the sheath is less than 0.025 mm
 5. Thesystem of claim 1 wherein the ultra-thin distal section of the sheath ismade from a heat shrinkable plastic.
 6. The system of claim 1 whereinthe ultra-thin distal section is made of nylon.
 7. The system of claim 1wherein the ultra-thin distal section of the sheath is made from asolvent swellable material.
 8. The system of claim 1 wherein theultra-thin distal section of the sheath is lubricity coated.
 9. Thesystem of claim 1 wherein the distal tip is more than 10 mm long. 10.The system of claim 1 wherein the distal tip is more than 20 mm long.11. The system of claim 1 wherein the distal tip is tapered from alarger diameter at its proximal end to a smaller diameter at its distalend.
 12. The system of claim 11 wherein the distal tip has an averagetaper of less than 4 degrees from its distal end to its proximal end.13. The system of claim 1 wherein the balloon angioplasty catheterfurther comprises a coaxially mounted elastomer band placed coaxiallyover the angioplasty catheter just proximal to the stent, the elastomerband being adapted to prevent the stent from sliding in a proximaldirection.
 14. The system of claim 13 wherein the elastomer bandincludes a high density material for increased radiopacity.
 15. Thesystem of claim 13 wherein the elastomer band has a proximal end and adistal end and the distal end of the proximal section of the sheath isadapted to provide distally directed push force against the proximal endof the elastomer band.
 16. The system of claim 13 wherein the balloonangioplasty catheter further comprises a coaxially mounted distalelastomer band placed coaxially over the angioplasty catheter justdistal to the stent, the distal elastomer band being adapted to preventthe stent from sliding in a distal direction.
 17. The system of claim 16wherein the distal elastomer band includes a high density material forincreased radiopacity.
 18. The system of claim 1 further comprising anelastomer securing tube having a proximal section and a distal section,the distal section being fixedly attached to the distal end of thedistal tip and the proximal section of the elastomer securing tube beingplaced over the distal end of the ultra-thin section of the sheath. 19.The system of claim 1 wherein the primary stenting system is anover-the-wire stent delivery catheter system.
 20. The system of claim 1wherein the primary stenting system is a rapid exchange stent deliverycatheter system.
 21. A pre-deployment configuration for a primarystenting system for placing a stent within a stenosis of a vessel in ahuman body, the system comprising: a flexible guide wire; a balloonangioplasty catheter having a distal portion, the balloon angioplastycatheter having an inflatable balloon located at its distal portion, theinflatable balloon having a proximal end and a distal end, the balloonangioplasty catheter also having a lumen through which the guide wirecan be slideably moved, the balloon angioplasty catheter also having adistal tip which extends in the distal direction from the distal end ofthe balloon to the distal end of the balloon angioplasty catheter, thedistal tip having a proximal end and a distal end, a stent coaxiallymounted around the inflatable balloon of the balloon angioplastycatheter; a sheath generally in the form of a cylindrical tube that iscoaxially located around the balloon angioplasty catheter with itscoaxially mounted stent, the sheath having an ultra-thin distal section,the ultra-thin distal section of the sheath being shrunk down onto thedistal portion of the balloon angioplasty catheter including itscoaxially mounted stent, the distal end of the shrunk down ultra-thindistal section being situated between the distal end of the angioplastyballoon and the distal end of the distal tip; and an elastomer securingtube having a proximal section and a distal section, the distal sectionbeing fixedly attached to the distal end of the distal tip of theballoon angioplasty catheter and the proximal section of the elastomersecuring tube being adapted to cover the distal end of the ultra-thinsection of the sheath, the sheath being adapted to be slideablyretracted in a proximal direction from under the securing tube.
 22. Thesystem of claim 21 wherein the wall thickness of the securing tube isless than 0.05 mm.
 23. The system of claim 21 wherein the wall thicknessof the securing tube is less than 0.025 mm.
 24. The system of claim 21wherein the wall thickness of the ultra-thin distal section of thesheath is less than 0.05 mm.
 25. The system of claim 21 wherein the wallthickness of the ultra-thin distal section of the sheath is less than0.025 mm
 26. The system of claim 21 wherein the ultra-thin distalsection of the sheath is made from a heat shrinkable plastic.
 27. Thesystem of claim 21 wherein the ultra-thin distal section is made ofnylon.
 28. The system of claim 21 wherein the securing tube is made ofnylon.
 29. The system of claim 21 wherein the ultra-thin distal sectionof the sheath is made from a solvent swellable material.
 30. The systemof claim 21 wherein the ultra-thin distal section of the sheath islubricity coated.
 31. The system of claim 21 wherein the distal tip ismore than 10 mm long.
 32. The system of claim 21 wherein the distal tipis more than 20 mm long.
 33. The system of claim 21 wherein the primarystenting system is an over the wire device.
 34. The system of claim 21wherein the primary stenting system is a rapid exchange stent deliverycatheter system.
 35. The system of claim 21 wherein the distal tip istapered from a larger diameter at its proximal end to a smaller diameterat its distal end.
 36. The system of claim 35 wherein the distal tip hasan average taper of less than 4 degrees from its distal end to itsproximal end.
 37. The system of claim 21 wherein the balloon angioplastycatheter further comprises a coaxially mounted elastomer band placedcoaxially over the angioplasty catheter just proximal to the stent, theelastomer band being adapted to prevent the stent from sliding in aproximal direction when the sheath is slideably retracted in a proximaldirection.
 38. The system of claim 38 wherein the elastomer bandincludes a high density material for increased radiopacity.
 39. Thesystem of claim 38 wherein the balloon angioplasty catheter furthercomprises a coaxially mounted distal elastomer band placed coaxiallyover the angioplasty catheter just distal to the stent, the distalelastomer band being adapted to prevent the stent from sliding in adistal direction after the sheath has been slideably retracted in aproximal direction.
 40. The system of claim 39 wherein the distalelastomer band includes a high density material for increasedradiopacity.
 41. A pre-deployment configuration for a primary stentingsystem for placing a stent within a stenosis of a vessel in a humanbody, the system comprising: a flexible guide wire; a balloonangioplasty catheter having a distal portion, the balloon angioplastycatheter having an inflatable balloon located at its distal portion, theinflatable balloon having a proximal end and a distal end, the balloonangioplasty catheter also having a flexible, distal tip having a distalend and a proximal end and also having a lumen through which the guidewire can be slideably moved; a stent coaxially mounted around theinflatable balloon of the balloon angioplasty catheter; a coaxiallymounted proximal elastomer band situated over the portion of the balloonangioplasty catheter that lies just proximal to the stent; and acoaxially mounted distal elastomer band situated over the portion of theballoon angioplasty catheter that lies just distal to the stent, theproximal and distal elastomer bands being adapted to prevent thecoaxially mounted stent from sliding off of the inflatable balloon ineither a proximal direction or a distal direction.
 42. The system ofclaim 41 wherein the distal tip is more than 10 mm long.
 43. The systemof claim 41 wherein the distal tip is more than 20 mm long.
 44. Thesystem of claim 41 wherein the distal tip has a gentle taper from alarger diameter at the proximal end of the distal tip to a smallerdiameter at the distal end of the distal tip the gently tapered distaltip and distal elastomer band together forming a smooth outer surface tofacilitate penetration of a tight stenosis.
 45. The system of claim 44wherein the gradually tapered distal tip has an average taper of lessthan 4 degrees from its distal end to its proximal end.
 46. The systemof claim 44 wherein the gently tapered distal tip, distal elastomer bandand proximal elastomer band are each lubricity coated.
 47. The system ofclaim 41 wherein the proximal and distal elastomer bands each include ahigh-density material for increased radiopacity.
 48. A pre-deploymentconfiguration for a primary stenting system for placing a stent within astenosis of a vessel in a human body, the system comprising: a flexibleguide wire; a balloon angioplasty catheter having a distal portion, theballoon angioplasty catheter having an inflatable balloon located at itsdistal portion, the inflatable balloon having a proximal end and adistal end, the balloon angioplasty catheter also having a flexible,gradually tapered distal tip having a distal end and a proximal end andalso having a lumen through which the guide wire can be slideably moved,the gradually tapered distal tip having a tapered proximal portion and atapered distal portion, both proximal and distal portions of thegradually tapered distal tip having a gradual taper; and a stentcoaxially mounted around the inflatable balloon of the balloonangioplasty catheter; a sheath generally in the form of an elongatedcylinder that is coaxially located around the balloon angioplastycatheter, the sheath having a proximal section and an ultra-thin distalsection, the proximal section of the sheath having a proximal end and adistal end, the ultra-thin distal section of the sheath having aproximal end and a distal end, the proximal end of the ultra-thin distalsection of the sheath being fixedly attached to the distal end of theproximal section of the sheath, at least a portion of the ultra-thindistal section being shrunk onto the stent and also onto the taperedproximal portion of the gradually tapered distal tip, the sheath beingadapted to be slideably retracted in a proximal direction so that thedistal end of the ultra-thin section of the sheath can be placedproximal to the balloon so as to allow balloon expansion for radialexpansion of the stent.
 49. The system of claim 48 wherein the wallthickness of the proximal section of the sheath is greater than the wallthickness of the ultra-thin distal section.
 50. The system of claim 48wherein the wall thickness of the ultra-thin distal section of thesheath is less than 0.05 mm.
 51. The system of claim 48 wherein the wallthickness of the ultra-thin distal section of the sheath is less than0.025 mm
 52. The system of claim 48 wherein the ultra-thin distalsection of the sheath is heat shrinkable.
 53. The system of claim 48wherein the ultra-thin distal section is made of nylon.
 54. The systemof claim 48 wherein the ultra-thin distal section of the sheath is madefrom a solvent swellable material.
 55. The system of claim 48 whereinthe ultra-thin distal section of the sheath is lubricity coated.
 56. Thesystem of claim 48 wherein the gradually tapered distal tip is lubricitycoated.
 57. The system of claim 48 wherein the ultra-thin distal sectionof the sheath is lubricity coated.
 58. The system of claim 48 whereinthe gradually tapered distal tip is more than 10 mm long.
 59. The systemof claim 48 wherein the gradually tapered distal tip is more than 20 mmlong.
 60. The system of claim 48 wherein the tapered proximal portion ofthe gradually tapered distal tip has a length that is at least 25% ofthe length of the gradually tapered distal tip.
 61. The system of claim48 wherein the gradually tapered distal tip has a taper of less than 4degrees from its distal end to its proximal end.
 62. The system of claim48 wherein the balloon angioplasty catheter has a coaxially mountedproximal elastomer band over the portion of the angioplasty balloon thatlies proximal to the stent, the proximal elastomer band being adapted toprevent the stent from sliding in a proximal direction.
 63. The systemof claim 62 wherein the proximal elastomer band includes a high densitymaterial for increased radiopacity.
 64. The system of claim 48 whereinthe balloon angioplasty catheter has a coaxially mounted distalelastomer band over the portion of the angioplasty balloon that liesdistal to the stent, the distal elastomer band being adapted to preventthe stent from sliding in a distal direction.
 65. The system of claim 64wherein the distal elastomer band includes a high density material forincreased radiopacity.
 66. The system of claim 62 wherein the balloonangioplasty catheter also has a coaxially mounted distal elastomer bandover the portion of the angioplasty balloon distal to the stent, thedistal elastomer band being adapted to prevent the stent from sliding ina distal direction, the ultra-thin distal section of the sheath beingshrunk down over the distal elastomer band, the proximal elastomer band,the stent and the tapered proximal portion of the gradually tapereddistal tip.
 67. The system of claim 66 wherein the proximal elastomerband and distal elastomer band each include a high density material forincreased radiopacity.
 68. The system of claim 48 further comprising anelastomer securing tube having a proximal section and a distal section,the distal section being fixedly attached to the tapered distal portionof the tapered distal tip and the proximal section of the elastomersecuring tube being placed snugly over the distal end of the ultra-thinsection of the sheath.